1. Field of the Invention
The present invention relates to a method and apparatus for packaging a roll of material. More specifically, the present invention relates to a method and apparatus for packaging a roll which is enveloped by a packaging sheet, the surface of which, before it comes into contact with the roll of material is, at least sectionally, made adhesive. The apparatus includes an unwinding station, pulling equipment, a sheet severer, gluing equipment and a winding station. The packaging sheet travels from the unwinding station, through the various pieces of equipment to the winding station.
2. Description of the Related Art
Methods and apparatuses for packaging material rolls, such as paper rolls, have been known for many years. Conventionally, the pulling equipment pulls the packaging sheet from a supply roll in the unwinding station and advances the packaging sheet toward a gap, which is formed by the roll of material that is to be packaged and a supporting roller carrying this roll. Generally, several rolls of packaging sheets, each of different width, are kept in the unwinding station to permit the width of the packaging sheet to vary in accordance with the width of the material that is to be packaged. Before the beginning of the packaging sheet reaches the gap, the side of the packaging sheet, which faces the roll of material is made adhesive. This side of the packaging sheet is hereinafter referred to as the "upper side". The roll of material, which is to be packaged, then rotates with the help of a plurality of supporting rollers. When the packaging sheet reaches the gap between the roll and the supporting roller, it is glued there to the external periphery of the roll of material. The roll of material thereafter carries the packaging sheet. The packaging sheet is severed from its supply roll with the help of a severer after the packaging sheet has enveloped the roll of material adequately. The rotation of the roll of material continues until the severed end of the packaging sheet is wound about the roll. The end of the packaging sheet must also be made adhesive so that it adheres to the periphery of the roll. Therefore, glue must be applied at the beginning and at the end of the packaging sheet to ensure a durable envelopment of the roll of material. Alternatively, it is also known to apply adhesive to the whole surface of the packaging sheet so that the individual layers or windings of the packaging sheet around the roll of material adhere to one another.
Typically, a glue or adhesive is applied to the surface of the packaging sheet to make this surface adhesive. Glue nozzles or rollers have been used for this purpose. This type of gluing section is structurally relatively complex and is therefore correspondingly expensive. The conventional gluing section requires a high degree of supervision, because the glue can easily cure when the machine is stopped. Moreover, the gluing section constantly represents a potential source of contamination. If the glue application is not set with sufficient accuracy, it can lead to unsatisfactory packaging results. For example, insufficient glue may be applied or contamination of the roll of material may occur because too much glue has been applied causing the glue to pour out. Too much glue or adhesive can lead to contamination of the face of the roll of material, which in turn causes the individual layers of the roll of material to adhere to one another.
U.S. Pat. No. 4,716,709 and the European Patent No. 0 499 954 A1 disclose a different method for making the surface of the packaging sheet adhesive. Here a packaging sheet is coated with a hot-melt adhesive, such as polyethylene. The surface of the packaging sheet is heated before the packaging sheet enters a gap between the roll of material and the supporting roller. As a result, the layer melts and becomes adhesive, which leads to adherence of the packaging sheet to the roll. The use of a plastic-coated packaging sheet, however, has the serious disadvantage that its renewed use is decidedly difficult. The adhesive layer can be detached from the packaging sheet only with appreciable effort and leads to a waste product, which can be disposed of only with difficulty. Moreover, this type of gluing requires very careful monitoring of the packaging process so that, when the packaging sheet stops, there will be no overheating, which could lead to ignition of the adhesive layer and/or of the packaging sheet. Furthermore, heating the packaging sheet leads to a corresponding increase in temperature in the outer layers of the roll of material, which is to be packaged, with a corresponding shift in the temperature and the moisture of the atmosphere surrounding the outer layers.